Head Gasket thickness selection
- Thread starter IJ.
- Start date
Ok im alittle confused the first time around i resurfaced the head but not the block used a 1.2mm MHG and it blew. Now i have it apart again and the block and head seems to be good, unwarped, and uncracked. Would it be necessary to have it resurfaced again?
I have sanded and cleaned the head and block really good, I used a metal ruler to see if its straight and it appears to be. is their another/better way to go about making sure its unwarped myself?
I have sanded and cleaned the head and block really good, I used a metal ruler to see if its straight and it appears to be. is their another/better way to go about making sure its unwarped myself?
kamikazemkiii;1440641 said:
You're kidding, right? You need a quality straight edge, long enough to extend beyond the ends of the block, or head, a set of feeler gauges, and then follow the procedure in the TSRM. Just cleaning the surface is not enough!
slow_yota;1440703 said:
Yes, if there's no damage. You have to remove the rivets, and totally clean off all the viton that's on it, and then use Permatex copper spray sealant on every surface. If by some chance the viton is in perfect condition, then you won't have to do anything to it, but I doubt it.
Considering that Cometic and other manufacturers make multiple thickness MHG's I doubt it would be an issue to find one to make up for material milled/decked however I was wondering if it is imperative to return the thinkness back to stock? I understand it will affect the quench and squish however I was under the impression that so long as I hook up my wideband and modify the fuel/timing parameters accordingly it shouldn't be a problem provided I have the necessary pistons to valve clearance and the pistons aren't protruding out of the cylinder bore? Perhaps returning the thickness back to stock is only necessary if I intend to use the stock parameters of the ECU? I just want to make sure prior to doing a rebuild.
Ok i am not familiar with rebuilding foreign engines (knowledable of american) Anyways i have a spare block and head that i am planning on rebuilding, not as a daily driver. I plan to build it from the bottom up inside and out. I have two mhg's one is the hks 1.2 and the other i believe is a 1.5, I know it would be a big jump to pull the rivets and make a 2.7 mhg, which would lower compression alot, but is it possible? Given i machine the block and head for use of an mhg? I plan to use bigger cams, and higher compression pistons.
I would go stand alone and upgrade fuel and air as necessary. Mind you this is only thoughts right now. just wanna know if it is is something that can actually be accomplished? any and all thoughts would be helpful.
I know by, if possible using this gasket set up i am gonna run into cam issues along with timing belt lengths and all that good stuff, but it will be done right if it can be.
I would go stand alone and upgrade fuel and air as necessary. Mind you this is only thoughts right now. just wanna know if it is is something that can actually be accomplished? any and all thoughts would be helpful.
I know by, if possible using this gasket set up i am gonna run into cam issues along with timing belt lengths and all that good stuff, but it will be done right if it can be.
I wouldn't try combining them, as the HKS stopper, at least, has three distinct parts, and I'm not sure about the other ones, but I wouldn't do it to my engine.
how do i tell the difference on them? the both look identical minus the steel thickness.
I take that back the one gasket might be a 2.0 it looks alot bigger than i originally thought. so maybe i can just work with that one and build around that?
I take that back the one gasket might be a 2.0 it looks alot bigger than i originally thought. so maybe i can just work with that one and build around that?
IJ.;1464459 said:
Sorry, I'm still learning specifics about the 7M and was basing my post on experience w/ other engines where it usually isn't good to have the pistons sticking out. I'll have to remember this during my own rebuild so I don't thinks somethings wrong when I notice them sticking out. On a side note, it appears this post also shows an easy way to tell how much the block might have been decked is to measure how far the piston sticks out of the cylinder.
Besides my ignorant statement regarding the piston sticking out, would the rest of my logic regarding the tune hold true?
Do us a favor and don't post unless you're 100% sure...the 7M is a very unforgiving engine when it comes to build specs. This forum is littered with the results of from guys using "I heard" or "that's they way they do it on <insert motor>". Suggest you do a lot of reading before you attempt a rebuild on this engine.
The quench is important on this engine due to the heat produced from the higher dynamic compression under boost. On a MHG less than stock thickness, the combination of reduced quench and increased compression under boost can cause it to detonate in a nanosecond. The 7M does not tolerate this well at all, especially with stock pistons.
Most guys will go with stock thickness or slightly more and bump boost.
The quench is important on this engine due to the heat produced from the higher dynamic compression under boost. On a MHG less than stock thickness, the combination of reduced quench and increased compression under boost can cause it to detonate in a nanosecond. The 7M does not tolerate this well at all, especially with stock pistons.
Most guys will go with stock thickness or slightly more and bump boost.
just to clarify with the superiors. in order for me to use an hks stopper 2.00mm (which im assuming its 2mm compressed) my specs should look like this?
115.67 - Head: deck to valve cover surface
198.2 - Block: deck to main bearing saddle
115.67 - Head: deck to valve cover surface
198.2 - Block: deck to main bearing saddle
Isnt it ok to a 2.0 hks stopper for lower compression. on a new head and block?? Im tryin to boost high. please say yes ! cus i already ordered it..LOL
What is the measurement of a compressed HKS 1.2mm HG? I have piston protrusion, and both the block and head were decked. My machinist is trying to find out what the compressed value of the HG is, to find out whether or not I have enough clearance, ultimately.
However...after reading on in this thread, I have picked up that I should maintain STOCK values, by running a thicker HG to give back material that was taken away when the block and head were machined. I have Wiseco pistons. The compression ratio has slipped my mind..but I know I kept it stock or as close to stock as possible when I bought them. Can someone explain to me, where exactly the main bearing "saddle" is? Is this the very "top" of where the crankshaft rides in the block?
However...after reading on in this thread, I have picked up that I should maintain STOCK values, by running a thicker HG to give back material that was taken away when the block and head were machined. I have Wiseco pistons. The compression ratio has slipped my mind..but I know I kept it stock or as close to stock as possible when I bought them. Can someone explain to me, where exactly the main bearing "saddle" is? Is this the very "top" of where the crankshaft rides in the block?
Okay thank you. Was not sure if thats what it meant, or if it was pre-compressed value. I'm going to grab some values from the garage tomorrow if I have time, and throw them up here. I'll have piston protrusion values...maybe you guys can help me decide what HG I should use. I have learned this motor is a very critical engine to rebuild and values/measurements are key. Hopefully some good advice can be had. Thanks again.
A steel head gasket doesn't compress.
The beads may flatten down but you don't measure it there anyway.
The beads may flatten down but you don't measure it there anyway.